Exposure to vibrating tools produces several characteristic disorders effecting tissues of the upper extremity, which collectively are termed the Hand-Arm Vibration Syndrome (HAVS). The National Institute of Occupational Safety and Health has recognized the importance of exposure and response relationships in hand-arm vibration by identification as one of three foci of the Musculoskeletal Disease Consortium (MSDC). This proposal represents the combined plan of investigators from Canada, Finland, Sweden and the United States to study four vibration-exposed cohorts in Europe and North America. They are the Suomossalmi forest worker cohort in Finland, the Volvo truck cab assembly workforce in Umea, the Electric Boat shipyard workforce in Connecticut, and Connecticut dental hygienists exposed to high frequency vibration. Dental hygienists appear to experience rapid onset injuries to mechanoreceptors in the fingers. The three industrial cohorts have been studied; their restudy reflects the intent to utilize existing exposure data, and to assure cohort participation where health effects have been quantified and where there are usable prior studies. The latter point is important because the proposed study period may be too brief to appreciate intra-subject change. Worksite selection reflects exposure variation and inclusion of impact (Volvo) and high frequency vibration (dental hygienists). Medical tests -- laser Doppler, cold challenge plethysmograpy, multi-frequency vibrometry, and fractionated digital nerve conduction -- are sophisticated and reflect physiologic understanding. Exposure assessment is the most complex component of this study. It includes vibratory and biomechanical assessment of cohort representatives and individual monitoring of daily work routines using individualized data loggers and sensor gloves. This level of detail, which has not been previously applied, reflects the necessity of assessing daily real time exposure corrected for biomechanical variables.